1. Field of the Invention
The present invention relates to a method for fabricating a wooden member whose outer periphery is an arc surface.
2. Description of the Related Art
Various members are fabricated to serve as wooden members whose outer peripheries are circular surfaces. For example, there is a wood-covered steering wheel at a steering wheel of a vehicle (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 11-180312). At this steering wheel, an outer periphery of an annular wheel ring, which is made of metal, is covered with a wooden member for ornamentation, improving tactile impression, etc. The wooden member has a structure in which a core hole is formed to pass along a circumferential direction of the wheel ring, and which is cut in half. The wooden member is assembled to the wheel ring by superposing and sandwiching the metal wheel ring with the wooden member.
When such a wooden member is to be fabricated, wooden original pieces with a rectangular cross-sectional form are placed in a pressure vessel, and are heated and softened for a predetermined duration in a high-temperature, high-pressure steam atmosphere. Next, the wheel ring is set between these wooden original pieces, and an outer peripheral surface of the wooden original pieces, which is provided with substantially right-angled angle portions, is pressed by a mold. At this time, in order to fix shape changes caused by the molding, this pressed state is maintained continuously for a predetermined duration. However, with such a method for fabricating wooden members, ratios of compression of, for example, angle portions tend to be high. As a result, after this processing, the wooden original piece is susceptible to the occurrence of shape deformation due to moisture absorption. Moreover, locations with higher compression ratios have denser coloring.
There is also a method in which curved surfaces are formed at corner portions of the outer peripheral face of a wooden original piece such that the cross-sectional form of the wooden original piece is substantially a ‘U’ shape. Thereafter, the outer peripheral surface of the wooden original piece is pressed in a mold, while large differences between thickness dimensions in radial directions of the ‘U’ shape are retained. However, with this method for fabricating wooden members, there may be cases in which curvature deformation is necessary, but processing to make portions whose shapes are to be altered larger or the like is troublesome. Moreover, cracking may occur during fabrication.